Beomaster 2400 cannot switch to FM5 !

11 replies
TR
traverso
Bronze
186 posts
Posted May 30, 2023 at 12:54 GMT ? Edited June 22, 2024 at 11:41 GMT
#687668
Hello, I am renovating a Beomaster 2400 and identified the following issue. When trying to activate FM 5, it does not happen and the 2400 remains on the actual selection, whatever. Although I may access any other entry than FM 5. The following done already replacement of:
  • the TR21 switching transistor,
  • IC5 and IC6 switching ICs,
  • all lamps as provided by Beoparts although not directly related
and also testing the relevant power supply 15V and 12,5V. The rest of the 2400 is working fine. Thank you for advise and tracks to explore. Cheers Alain  
DI
Dillen
BronzeModerator
12821 posts
Posted May 30, 2023 at 13:10 GMT
#701935
Will it switch to FM5, if you touch the FM5 contact pin on the main PCB directly with your finger? Martin
TR
traverso
Bronze
186 posts
Posted May 30, 2023 at 13:36 GMT
#701936
No it does not if I am on an other entry However, it starts the 2400 when in stand by but does not allow to use FM5 the corresponding lamp is not lit, but in that case I may switch to any other input   Alain
DI
Dillen
BronzeModerator
12821 posts
Posted May 30, 2023 at 13:59 GMT ? Edited May 30, 2023 at 14:01 GMT
#701937
So the FM5 lamp never lights up - even while touching the FM5 pad? Was this problem present also before you started work? Before you replaced lamps? Martin
TR
traverso
Bronze
186 posts
Posted May 30, 2023 at 14:51 GMT
#701938
Yes it was always there (By the way I measured the lamps they are 18 Ohms each instead of 12/14 Ohms as a consequence, the voltage reference for muting measured at R3, 33Ohms of PCB 5 is no longer 2,5 Volts but 1,9 Volt)
DI
Dillen
BronzeModerator
12821 posts
Posted May 30, 2023 at 15:40 GMT
#701939
Since it does switch on, we can assume that the sensor pad circuit around TR21 is working. The problem must be somewhere from R126 up to IC6. A broken copper trace, perhaps? Have you checked R126? Those high-ohm resistors can go way high or even completely open. You could lift one end of R122 and R126 respectively and cross their connections to see if the FM5 pad will then give you FM4 and the problem moved to the FM4 pad. Martin
MA
Madskp
Gold
1759 posts
Posted May 30, 2023 at 17:47 GMT
#701943
Is the P5 button located on another PCB like it is in a BM3000? in that case I had similar trouble with a BM3000 where the problem was the soldered ribbon cable connections where they meet the PCB where there was one bad solder point, and one case where one of the wires going through the PCB was bent a little and short circiuted to one of the other pins

Location: Denmark

TR
traverso
Bronze
186 posts
Posted May 30, 2023 at 19:36 GMT
#701947
The signalling only is on an other PCB not the commands
TR
traverso
Bronze
186 posts
Posted May 31, 2023 at 12:07 GMT ? Edited May 31, 2023 at 12:08 GMT
#701951
Yes! I used FM4 to activate FM5 and it works as follows:
  • the R122 and R126 lifted from the IC6 side
  • the R122 connected in place of R126 on IC6 side
So the issue is between TR21 and the IC6, to confirm I have to replace this R126 or look for broken copper track Thanks a lot Martin
TR
traverso
Bronze
186 posts
Posted May 31, 2023 at 15:09 GMT
#701953
The culprit was R126 measured 40 MOhms
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